G. Wilde
Department of Entomology, Kansas State University, Manhattan, KS USA 66506-4004

Corn Acreage:
Control Area = ca. 1290 a. (11 separate producers over a 2 section x 2 section area)
          1998 Acreage = ca. 1400 a. (12 producers)
          1997 Acreage = ca. 1307 a. (11 producers)

Managed Area = ca. 4560 a. (36 separate producers over a 4 section x 4 section area)
          1998 Acreage = ca. 4850 a (36 producers)
          1997 Acreage = ca. 4246 a. (36 producers)

Number of Cornfields:

Survey Method:
Pherocon AM yellow sticky traps - 12 / field for 1997, 98, and 99. Plant count - visual inspection for western corn rootworm (WCR) beetles on 5 plants in 4 separate field locations. All counts conducted at least weekly in every field that had a sticky trap weekly average of 20 beetles.

Treatment Thresholds:
> 25 WCR's per sticky trap per week (average of the 12 traps). This was lower than the threshold we used in 1997 and 98 (>35 WCR's per sticky trap per week). We decided to lower the threshold because of the large number of beetles in 1999 fields. Thresholds from visual plant inspections remained the same for all three years: >0.6 WCRs per plant.

WCR Infestation Level:
Control Area (1999): 14 / 21 fields exceeded treatment threshold (1100 / 1290 a. = 85.3%)
          a. exceeding threshold / total acres: 1st yr. corn = 120 / 290 (41.4%)
          a. exceeding threshold / total acres: 2nd yr. corn 560 / 580 (96.6%)
          a. exceeding threshold / total acres: 3rd yr. corn 420 / 420 (100%)

Managed Area (1999): 38 / 80 fields exceeded treatment threshold (2310 / 4560 a. = 50.7%)
          a) exceeding threshold / total acres: 1st yr. corn = 0 / 1230
          a) exceeding threshold/total acres: 2nd yr. corn 580 / 1090 (53.2%)
          a) exceeding threshold / total acres: 3rd yr. corn 1730 / 2240 (77.2%)

Treatment Timing:
>25 WCR's per sticky trap and/or 0.6 WCR's per plant (from visual inspections) and observation of the first obviously gravid females. In 1997 and 1998 the treatment threshold was >35 WCRs and 35% of the females obviously gravid (1997) and 15% gravid in (1998).

WCR Adult Emergence:
1999 - 14 fields were monitored (4 in the control area and 10 in the managed area) with 2 to 14 cages per field (64 cages total) depending upon field size. All cages were placed in the fields by 18 June and checked every 3 days. The first adults were captured on 25 June from the managed area and 29 June from the control area. The last adults were captured in the emergence cages on 10 Aug in both the managed and control areas. Peak emergence occurred between 6-16 July in both areas (72.4% of the adults were captured during this time). Almost twice as many beetles were captured from emergence cages in 1999 with fewer cages than in 1998 (64 to 100, respectively).

Number of beetles which could possibly be produced utilizing emergence cage data:

Root Ratings:
Managed Area: Mean root ratings from 1999 fields which exceeded the treatment threshold in 1998 and were treated with SLAM was 1.96. Mean root rating from 1999 fields that did not exceed the treatment threshold in 1998 and were not treated was 1.71 (this excludes 1 st year cornfields).

Control Area:
Mean root rating from 1999 fields that exceeded the treatment threshold in 1998 was 1.78. Mean root rating from 1999 fields that did not exceed the treatment threshold in 1998 was 1.92 (this excludes 1 st year comfields).